The present invention relates to a common shutter blade and lens focusing system drive for a photographic camera, in general, and to such a drive for a single lens reflex camera employing a scanning blade type shutter, in particular.
Photographic apparatus employing shutter blade mechanisms, in general, and scanning blade shutters, in particular, as well as a lens mechanism that may be automatically focused in accordance with a rangefinder-determined camera-to-subject distance are well known in the art. A camera employing a scanning blade shutter and a lens mechanism responsive to a rangefinder-determined subject distance signal is described in, for example, U.S. Pat. No. 4,192,587, entitled "Proportioned Fill Flash", by A. G. La Rocque, et al, issued Mar. 11, 1980, in common assignment herewith. For convenience, the disclosure in said LaRocque et al patent is specifically incorporated herein by reference.
Scanning shutter blade mechanisms are normally driven from a scene light blocking position toward a maximum aperture defining position and thereafter returned to their initial scene light blocking position during an exposure interval. Such scanning blade shutter mechanisms generally comprise a pair of scanning blade shutter elements each having a primary aperture therethrough. The shutter blade elements overlap for reciprocal movement with respect to each other. This movement drives the primary aperture into overlapping relationship with each other so as to define a progressively increasing and then decreasing effective primary aperture. The shutter blade mechanisms are normally driven by a spring and solenoid arrangement as shown in La Rocque et al, supra, or by a microcomputer controlled stepper motor incorporating a digitally encoded scanning blade position sensor as shown, for example, in U.S. Pat. No. 4,325,614, entitled "Exposure Control System With Shutter Operation Controlled by a Microcomputer", by D. L. Grimes, issued Apr. 20, 1982, in common assignment herewith.
Autofocus cameras of the aforementioned type generally embody a motor driven objective lens mechanism which must be stopped at an appropriate focal position corresponding to a previously determined camerato-subject distance. In such cameras, it is desirable to provide a lens position encoder system to identify the instantaneous focal position of a lens element driven by said lens mechanism as it is moved through its plurality of different focal positions in order to precisely position the lens element at a previously determined object-distance-related focal position as shown, for example, in La Rocque et al, supra.
In prior adjustable focus lens cameras employing scanning shutter blades, the objective lens and shutter blade mechanisms are driven by a common drive either that sequentially drives the objective lens and the shutter blades or are driven by separate shutter blade and lens drive means. U.S. Pat. No. 4,278,340 to Toyama et al is an example of such a sequential lens and shutter blade drive and U.S. Pat. No. 4,199,244 to Shenk is an example of a camera employing separate shutter blade and lens drives. In addition, if an encoder system were to be employed in such cameras to determine the instantaneous focal position of the movable lens element as in, for example, La Rocque et al, supra, and the instantaneous blade position of the scanning shutter blades as in, for example, Grimes, supra, the prior art teaches the use of separate encoders for each such position sensing function. The use of duplicate drive means and encoders in an autofocus camera necessarily increases camera cost, size and complexity.
It is a primary object of the present invention, therefore, to provide a single or common drive for a photographic camera that is capable of driving the movable element of an adjustable focus lens to a previously determined lens focal position and of driving a scanning blade type shutter mechanism during an exposure interval.
It is another object of the present invention to provide a rangefinder-derived signal-responsive common drive that is capable of simultaneously driving both the shutter and focusing mechanisms in a single lens reflex camera.
It is a further object of the present invention to provide a single position-encoder that is capable of determining both the instantaneous blade position of a shutter blade mechanism and the instantaneous focal position of the movable lens element in an adjustable focus lens camera.
Other objects and/or advantages of our invention will be made readily apparent by referring to the preferred embodiment thereof described in detail below.